Power has been restored to more than 1,600 customers who were briefly without power Tuesday night in San Francisco's Richmond District, and PG&E investigators were still trying to determine the cause of the outage, which struck at 7:30 p.m. and ended 45 minutes later.

The affected area was north of Geary Boulevard and bounded by Fourth Avenue and Park Presidio Boulevard, PG&E spokesperson Jana Morris said Tuesday evening. Initially 2,600 customers were affected, but the utility restored power to 1,000 within roughly a half hour.

Initial reports from residents were that the outage occurred shortly after a car struck a utility poll, Morris said, but investigators have not been able to find any such accident.